6127 International Standard OSI) Chromium ores - Determination of phosphorus content - Reduced molybdophosphate photometric method Minerais de chrome -Dosage du phosphore -- Methode photometrique au molybdophosphate reduit Firstedition1981-03-15 127-1981(E) UDC 553.461 : 543.42 : 546.18 Ref.No.ISO 6127-1981(E) Descriptors : chromate minerals, chemical analysis, determination of content, phosphorus, spectrophotometric analysis. Foreword so (the International Organization for Standardization) is a woridwide federation of national standards institutes (Iso member bodies). The work of developing Inter- national Standards is carried out through Iso technical committees. Every member body interested in a subject for which a technical committee has been set up has the right to be represented on that committee, International organizations, governmental and non-governmentai, in liaison with Iso, also take part in the work. the member bodies for approval before their acceptance as International Standards by the Iso Council. International Standard ISO 6127wasdeveloped byTechnical Committee ISO/TC 65, Manganese and chromium ores, and was circulated to the member bodies in January 1980. It has been approved by the member bodies of the following countries : Australia France Poland Austria Hungary Romania Buigaria eipul South Africa, Rep of China Italy United Kingdom Czechoslovakia Japan USSR Egypt, Arab Rep. of Korea, Dem. P. Rep. of No member body expressed disapproval of the document. ? InternationalOrganizationforStandardization,1981 Printed in Switzerland Coovriaht International Oraanization for Standardization INTERNATIONALSTANDARD ISO6127-1981(E) Chromium ores -- Determination of phosphorus content -- Reduced molybdophosphate photometric method WARNING G-Attention is drawn to the dangers involved in the use of some reagents (see the notes to sub-clauses 4.3 and 4.8). Scope and field of application Formation of the yellow molybdophosphate complex, followed by its reduction to the blue complex with iron(ll) ions in the This International Standard specifies a reduced molyb- presence of hydrochloric acid and hydroxylammonium dophosphatephotometricmethodforthedeterminationofthe chloride, by addition of iron(lll) nitrate, ammonia, hydroxyl- phosphorus content of chromium ores. ammonium chloride, hydrochloric acid and ammonium molyb- date solutions to an aliquot portion of the test solution. The method is applicable to products having a phosphorus con- tent of 0,002 to 0,1 % (m/m). Photornetric measurement of the resultant complex using a spectrophotometer or photoelectric absorptiometer. This International Standard should be read in conjunction with ISO6629. 4 Reagents Reference 4.1 Nitric acid, g 1,40 g/ml. ISO6629， Chromiumoresandconcentrates-- Methods of 4.2 Nitric acid, diluted 1 + 9. chemical analysis -General instructions.1) 4.3 Perchloric acid, g 1,50 g/ml. 3Principle NOTE - Risk of poisoning by inhalation, swallowing or contact with the skin. Handle in an efficient fume cupboard, away from exposed flames, etc. Avoid inhalation of fumes and contact with skin, eyes and Decomposition of a test portion, either clothing. a) by treatment with nitric and perchloric acids, or 4.4 Sodium peroxide,free from phosphorus. b) by fusion with sodium peroxide, followed by leaching with water. 4.5 Hydrochloric acid, Q 1,19 g/ml. Removal of.chromium by distillation as chromyl chloride. Filtra- tion of the residue. Removal of silicic acid by volatilization with 4.6 Hydrochloric acid,diluted1+1. nitric and hydrofluoric acids. Fusion of the residue with sodium carbonate or a mixture of sodium carbonate,sodiumtetra- 4.7 Hydrochloric acid, diluted 1 + 100. borate and sodium nitrate; extraction of the fused melt with nitric acid and combining with the main solution. 4.8 Hydrofluoric acid, 40 % (m/m) solution. Separation of phosphorus from chromium by co-precipitation NOTE - Risk of poisoning by inhalation, swallowing or contact with with iron(ll) hydroxide